Try an HD valance from your year model. That's what I run and it has good airflow. The hole that's in the front can be trimmed on the back side and make the hole bigger with out looking odd. Looks like stock that's why I went with it.

 

The HD valance looks the same. Would a Sierra valance fit to the bottom my Silverado bumper? They have a slot in the middle that would work.

 

looks the same as what? it has a long slotted hole in the center.

the bumpers are different on the gmc from the chevy and iirc the valances will not interchange.

 

like this.

 

The HD valance looks the same as the non-HD valance for my year and model, at least according to what I can find on google and rockauto. I can't seem to find the one in your picture for sale.

 

I'll try to find the part number I ordered for you.

 

If I remember right, your truck is an 01 and those have like 4 recessed, rectangle areas in the lower valance?? Just cut those out and should be enough air flow. That's what we did with Thunder550's 01 back in the day.

 

There aren't and recessed holes in the lower valance in front of the intercooler. Maybe you're thinking of the Tahoe valance? Here's a pic of spoolin's truck, I have the same valance, also with those 4 holes in the bumper cap opened up.

http://image.truckinweb.com/f/featur...front-view.jpg

 

i called torquewrench when he worked at the dealer. i could have sworn it was a 2001 2500hd or 3500hd with the dmax. i can't find the part number right now.

 

I think it's 15709110, and it ain't cheap!